L-arginine has two main effects: it turns into nitric oxide, and it helps the body build protein.

 L-arginine has two main effects: it turns into nitric oxide, and it helps the body build protein.

Nitric oxide is involved in the dilation of blood vessels. Having enough helps blood vessels open up, increasing blood flow.

Improved blood flow can resultTrusted Source in more oxygen and nutrients reaching the muscles, and may help the body to remove waste products, such as lactate and ammonia, from those muscles more quickly.

There are many other claims about the health benefits of L-arginine, but not all of them have support from scientific studies.

Some of the potential benefits that do have evidence include:

• Improving athletic performance: The results of a 2020 review and meta-analysisTrusted Source suggest that L-arginine supplements may have a positive effect on aerobic and anaerobic exercise performance when a person takes them 60 to 90 minutes prior.
• Reducing high blood pressure: A 2021 meta-analysisTrusted Source suggests L-arginine may help to reduce high blood pressure. This appears to work more effectively in females than in males.
• Delaying type 2 diabetes: A 2017 studyTrusted Source tested L-arginine supplementation in middle aged adults with metabolic syndrome and impaired glucose tolerance. The authors found that the supplement may help to delay the onset of diabetes for “a long period”.
• Treating peripheral arterial disease (PAD): Because of L-arginine’s effects in widening blood vessels, it may help those with PAD. A small study found that L-arginine infusion improved the function of narrowed blood vessels, but more research is necessary.
• Treating pregnancy complications: A 2021 reviewTrusted Source of 45 previous studies found that L-arginine may help to to reduce preeclampsia or gestational hypertension during pregnancy.
• Preventing necrotizing enterocolitis: L-arginine may help prevent necrotizing enterocolitis, a serious illness in premature infants, according to a 2017 studyTrusted Source.

More research is necessary to evaluate L-arginine’s potential to heal woundsTrusted Source faster or improve breathingTrusted Source in people with illnesses affecting the respiratory system.

People can get L-arginine as part of their regular diet. Some people take L-arginine as a supplement. However, as with any supplement, a person should talk to a doctor before use.

Side effects of L-arginine

While L-arginine supplements may have some benefits, they can sometimesTrusted Source cause side effects, such as nausea or diarrhea.

In certain situations L-arginine may also result in some more serious effects, such as:

• reduced blood pressure, which may be a problem for people who already have low blood pressure
• interactions with certain medications
• increasing the growth of specific types of tumor
• potential kidney damage with long-term use, although more research in humans is necessary to confirm this

Always consult a doctor or dietitian before taking any new dietary supplement.

Safe daily intake

According to the National Institutes of Health (NIH)Trusted Source, L-arginine doses of up to 9 grams (g) per day are usually safe for several weeks, but larger doses may cause adverse effects.

Additionally, the effects of long-term L-arginine supplementation are not clear in humans.

The dosage that is beneficial for a person may depend on their age, existing health conditions, and the reason for supplementation.

The Food and Drug Administration (FDA) does not check the safety or effectiveness of dietary supplements, so it is important to choose a reputable brand that undertakes third-party testing to prove the purity and quality of their products.

Drug interactions

L-arginine supplements and medications may interact with drugs that lower blood pressure, including sildenafil (Viagra).

It may also enhance the effects of some medications, which could result in adverse effects.

People who take medications or have pre-existing health conditions should consult a doctor before taking additional L-arginine.